docs: def update(self, pbar):
          'Updates the widget with the current SI prefixed speed.'
  
          if pbar.seconds_elapsed < 2e-6 or pbar.currval < 2e-6:  # =~ 0
              scaled = power = 0
          else:
              scaled, power = self._speed(pbar)
  
          return self.format % (scaled, self.prefixes[power], self.unit)